US3784678A - Process for removing iron from phosphoric acid - Google Patents
Process for removing iron from phosphoric acid Download PDFInfo
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- US3784678A US3784678A US00182240A US3784678DA US3784678A US 3784678 A US3784678 A US 3784678A US 00182240 A US00182240 A US 00182240A US 3784678D A US3784678D A US 3784678DA US 3784678 A US3784678 A US 3784678A
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- phosphoric acid
- barium
- ions
- iron
- acid
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title abstract description 158
- 229910000147 aluminium phosphate Inorganic materials 0.000 title abstract description 79
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title abstract description 62
- 229910052742 iron Inorganic materials 0.000 title abstract description 31
- 238000000034 method Methods 0.000 title abstract description 30
- 230000008569 process Effects 0.000 title abstract description 27
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 abstract description 11
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 abstract description 11
- 150000001553 barium compounds Chemical class 0.000 abstract description 6
- 235000011007 phosphoric acid Nutrition 0.000 description 77
- 239000002253 acid Substances 0.000 description 20
- 229910001422 barium ion Inorganic materials 0.000 description 18
- 239000002244 precipitate Substances 0.000 description 14
- -1 sulphate ions Chemical class 0.000 description 14
- 239000003960 organic solvent Substances 0.000 description 13
- 229910021653 sulphate ion Inorganic materials 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 239000000243 solution Substances 0.000 description 9
- 229910019142 PO4 Inorganic materials 0.000 description 7
- 235000021317 phosphate Nutrition 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 238000001914 filtration Methods 0.000 description 6
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 5
- 239000003729 cation exchange resin Substances 0.000 description 5
- 239000000706 filtrate Substances 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 5
- 239000010452 phosphate Substances 0.000 description 5
- 229910052788 barium Inorganic materials 0.000 description 4
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 4
- AYJRCSIUFZENHW-UHFFFAOYSA-L barium carbonate Chemical compound [Ba+2].[O-]C([O-])=O AYJRCSIUFZENHW-UHFFFAOYSA-L 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical compound [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 description 3
- 229910001863 barium hydroxide Inorganic materials 0.000 description 3
- WAKZZMMCDILMEF-UHFFFAOYSA-H barium(2+);diphosphate Chemical compound [Ba+2].[Ba+2].[Ba+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O WAKZZMMCDILMEF-UHFFFAOYSA-H 0.000 description 3
- 230000001419 dependent effect Effects 0.000 description 3
- 238000004821 distillation Methods 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 239000008346 aqueous phase Substances 0.000 description 2
- CJDPJFRMHVXWPT-UHFFFAOYSA-N barium sulfide Chemical compound [S-2].[Ba+2] CJDPJFRMHVXWPT-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003456 ion exchange resin Substances 0.000 description 2
- 229920003303 ion-exchange polymer Polymers 0.000 description 2
- 150000002576 ketones Chemical class 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000012074 organic phase Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000005191 phase separation Methods 0.000 description 2
- 150000003016 phosphoric acids Chemical class 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- DLYUQMMRRRQYAE-UHFFFAOYSA-N tetraphosphorus decaoxide Chemical compound O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 150000005325 alkali earth metal hydroxides Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- AYJRCSIUFZENHW-DEQYMQKBSA-L barium(2+);oxomethanediolate Chemical compound [Ba+2].[O-][14C]([O-])=O AYJRCSIUFZENHW-DEQYMQKBSA-L 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 102000004196 processed proteins & peptides Human genes 0.000 description 1
- 108090000765 processed proteins & peptides Proteins 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/46—Preparation involving solvent-solvent extraction
- C01B25/461—Preparation involving solvent-solvent extraction the phosphoric acid present in the medium obtained after reaction being first extracted from the liquid phase formed or separated then re-extracted as free acid by using water or as a phosphate by using a basic compound
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/234—Purification; Stabilisation; Concentration
- C01B25/237—Selective elimination of impurities
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/46—Preparation involving solvent-solvent extraction
- C01B25/461—Preparation involving solvent-solvent extraction the phosphoric acid present in the medium obtained after reaction being first extracted from the liquid phase formed or separated then re-extracted as free acid by using water or as a phosphate by using a basic compound
- C01B25/462—Preparation involving solvent-solvent extraction the phosphoric acid present in the medium obtained after reaction being first extracted from the liquid phase formed or separated then re-extracted as free acid by using water or as a phosphate by using a basic compound the extracting agent being alcohol or a mixture of alcohols
Definitions
- This invention relates to the purification of phosphoric acid and more particularly to a process for removing 1ron from phosphoric acid.
- Phosphoric acid is generally manufactured in accordance with two processes.
- phosphoric acid is produced from phosphate ore by contact with a strong mineral acid, such as sulfuric acid.
- Phosphoric acid thus produced contains relatively many impurities since constitutents of the phosphate ore form soluble salts with the mineral acid.
- elemental phosphorus produced by the electrothermic reduction of a phosphate ore is oxidized to phosphorus pentoxide which is absorbed by water to form phosphoric acid.
- Relatively pure phosphoric acid is produced by this second process.
- Phosphoric acid produced in accordance with former process generally requires purification, especially if the acid is to be used in the manufacture of special optical lenses.
- Methods for purifying phosphoric acid produced by contacting a phosphate ore with a strong mineral acid include extraction methods wherein the impure phosphoric acid is admixed with an organic solvent which is immiscible with water.
- the phosphoric acid after admixing, is absorbed by the organic solventand upon phase separation, the oragnic phase is separated from the aqueous phase. Thereafter, the organic solvent is admixedwith pure water to reextract the phosphoric acid therefrom to produce substantially pure phosphoric acid.
- Organic solvents include the higher, water-immiscible alcohols, ester, ethers and the like.
- Another extraction method is based upon the solubility difference of phosphoric acid in Water and in an organic solvent at various temperatures.
- impure phosphoric acid and an organic solvent are admixed at a low temperature whereas the phosphoric acid is more soluble in organic solvent.
- the organic phase is separated from the aqueous phase and the temperature of the organic phase raised thereby freeing phosphoric acid.
- the acid is neutralized with an alkali metal, alkali earth metal and/or ammonium hydroxide (or related carbonates). Accordingly, the heavy metals and alkali metals precipitate as hydroxides and/or phosphates which are separated from the salt solution by filtration. It is known that hydroxide precipitates are poorly filtered from concentrated salt solutions and that a portion of the precipitate may wind up in the filtrate in the form of peptides. Additionally, phosphorous losses are relatively high since the precipitate of this type may only be poorly and incompletely washed.
- An object of this invention is to provide an improved process for purifying phosphoric acid.
- Another object of this invention is to provide an improved process for effectively removing iron from phosphoric acid.
- a further advantage of the present invention resides in the fact that precipitation of barium can be successfully conducted in phosphoric acid diluted with an organic solvent miscible with phosphoric acid and water in all proportions, such as water-soluble aliphatic alcohols and/ or ketones. Dilution of concentrated phosphoric acid with such an organic solvent facilitates separation of the precipitate, since it is easily filtered. The reconcentration of the purified phosphoric acid from such a diluted solution is accomplished with considerably less consumption of energy than when using water alone.
- the amount of solvent in the phosphoric acid can vary over a wide range. It has been noted that the process works best if the P 0 content of the dilute phosphoric acid is between about 5 and 30 weight percent and the amount of solvent is between about 40 and 90 weight percent. 7
- the removal of iron from the phosphoric acid can in principle be accomplished with any water soluble barium compounds.
- slightly soluble barium compounds are suitable as cannot possibly form a solution but permit barium ions to dissolve into phosphoric acid.
- the barium compounds used include barium hydroxide, barium phosphate, barium carbonate and barium sulphide.
- the distinguishing features of the process according to the present invention is the removal of iron from phosphoric acid by precipitation with barium ions in the presence of sulphate ions.
- the precipitation process of the invention is not limited to phosphoric acids which contain the contaminants named, but may also be used in the treatment of other phosphoric acids containing other impurities as well as iron and sulphate ions.
- the amount of barium used is in excess with respect to the amount of sulphate. The effect achieved is dependent as much on the sulphate concentration as on an excess of barium ions.
- the amount of sulfate ions should be in the range of 0.01 to 0.5 weight percent with respect to the P 0 content of the phosphoric acid, and the amount of barium ions should be 2 to 20 times in excess of the amount of sulphate ions.
- the barium ions remaining in the acid because of the necessity of excess barium ions are removed from the acid by passing the acid through a strongly acid cation exchange resin after filtration.
- the thus purified phosphoric acid may be brought to final concentration, which in the case of organic solvents, is accomplished by distillation.
- Example I A technical grade phosphoric acid prepared by the wet process subsequently purified contains 52 weight percent P 0 0.05 weight percent Fe ions and 0.2 weight percent H 80 10 kilograms of this acid are diluted with 20 kilograms of acetone with 200 grams of dry barium carbonate thereafter introduced with vigorous stirring. After a period of 5 minutes, the precipitate is separated from the filtrate by filtration and the filtrate passed through a strongly acid cation exchange resin in the H+ form and is subsequently distilled. In the distillation vessel there remained 9.3 kilograms of a phosphoric acid having a P 0 content of 53.0 weight percent, an iron content of 0.003 weight percent and a sulphate content of 0.001 weight percent.
- Example III A technical grade phosphoric acid produced by the wet process and previously purified contains 48.0 weight percent P O 0.03 weight percent Fe and 0.1 weight percent H 50 10 kilograms of the acid are diluted with 30 kilograms of water. Into a stirred container, there are added 51 -grams of barium hydroxide dissolved in 200 milliliters of carbonatet-free water to the dilute phosphoric acid. After 10 minutes, the precipitate is separated from the solution by filtration with the filtrate being passed through a strongly acid cation exchange resin in the H+form. The filtration time is limited. 11.0 kilograms of a phosphoric acid are recovered with a P 0 content of 41 weight percent and a Fe content of 0.0015 weight percent. Sulphate ions are not demonstrable.
- a process for removing iron ions from phosphoric acid having iron and sulfate ions which comprises:
- step (b) adding barium ions to the solution resulting from step (a), the amount of barium ions added being of from two to twenty times in excess of the amount necessary to precipitate the sulfate ions whereby a precipitate is formed;
- barium compound acting as a source of barium ions is selected from the group comprising barium carbonate, barium phosphate, barium hydroxide and barium sulfide.
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Analytical Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Removal Of Specific Substances (AREA)
Abstract
A PROCESS FOR REMOVING IRON FROM PHOSPHORIC ACID. A BARIUM COMPOUND IS ADDED TO THE PHOSPHORIC ACID INCLUDING SULFATE IONS TO PRECIPITATE BARIUM SULFATE WHEREBY THE IRON CONTENT OF THE PHOSPHORIC ACID IS SUBSTANTIALLY REDUCED.
Description
United States Patent O 3,784,678 PROCESS FOR REMOVING IRON FROM PHOSPHORIC ACID Klaus Beltz, Budenheim (Rhine), Klaus Frankenfeld,
Kirberg, Taunus, and Karl Gotzmann, Budenheim (Rhine), Germany, assignors to Chemische Fabrik Budenheim No Drawing. Filed Sept. 20, 1971, Ser. No. 182,240 Claims priority, application Germany, Sept. 25, 1970,
Int. Cl. C01b 25/16 US. Cl. 423-321 6 Claims ABSTRACT OF THE DISCLOSURE A process for removing iron from phosphoric acid. A barium compound is added to the phosphoric acid including sulfate ions to precipitate barium sulfate whereby the iron content of the phosphoric acid is substantially reduced.
This invention relates to the purification of phosphoric acid and more particularly to a process for removing 1ron from phosphoric acid.
BACKGROUND OF THE INVENTION Phosphoric acid is generally manufactured in accordance with two processes. In one process, phosphoric acid is produced from phosphate ore by contact with a strong mineral acid, such as sulfuric acid. Phosphoric acid thus produced contains relatively many impurities since constitutents of the phosphate ore form soluble salts with the mineral acid. In the other process, elemental phosphorus produced by the electrothermic reduction of a phosphate ore is oxidized to phosphorus pentoxide which is absorbed by water to form phosphoric acid. Relatively pure phosphoric acid is produced by this second process. Phosphoric acid produced in accordance with former process generally requires purification, especially if the acid is to be used in the manufacture of special optical lenses.
Methods for purifying phosphoric acid produced by contacting a phosphate ore with a strong mineral acid include extraction methods wherein the impure phosphoric acid is admixed with an organic solvent which is immiscible with water. The phosphoric acid, after admixing, is absorbed by the organic solventand upon phase separation, the oragnic phase is separated from the aqueous phase. Thereafter, the organic solvent is admixedwith pure water to reextract the phosphoric acid therefrom to produce substantially pure phosphoric acid. Organic solvents include the higher, water-immiscible alcohols, ester, ethers and the like.
- Another extraction method is based upon the solubility difference of phosphoric acid in Water and in an organic solvent at various temperatures. Thus, impure phosphoric acid and an organic solvent are admixed at a low temperature whereas the phosphoric acid is more soluble in organic solvent. After phase separation, the organic phase is separated from the aqueous phase and the temperature of the organic phase raised thereby freeing phosphoric acid.
With extraction methods, an equilibrium is established between phases which applies not only to phosphoric acid but also to dissolved impurities. Consequently, the purification achieved is dependent upon the coefiicients of separation for the components as well as the number of extraction steps, and within the limits of prevailing technology is only partially satisfactory. While phosphoric acid produced by the electrothermic reduction process is relatively pure, it is known that with storage and transportation, that impurities become dissolved in such phosphoric acid. Iron is the most common impurity found in thermic acid, and as hereinbeforementioned is undesirable where the phosphoric acid is to be utilized in a process for the manufacture of special optical lenses.
Should it be desirable to produce phosphates from phosphoric acid produced by the first method, the acid is neutralized with an alkali metal, alkali earth metal and/or ammonium hydroxide (or related carbonates). Accordingly, the heavy metals and alkali metals precipitate as hydroxides and/or phosphates which are separated from the salt solution by filtration. It is known that hydroxide precipitates are poorly filtered from concentrated salt solutions and that a portion of the precipitate may wind up in the filtrate in the form of peptides. Additionally, phosphorous losses are relatively high since the precipitate of this type may only be poorly and incompletely washed.
Even the use of ion exchange resins for removing iron from phosphoric acid is not satisfactory, since iron will form, in part, phosphate complexes which will not be effectively removed by ion exchange resins. Consequently, prior to using phosphoric acid where high purity phosphoric acid is required, it is necessary to repurify commercially available phosphoric acid.
OBJECTS OF THE INVENTION An object of this invention is to provide an improved process for purifying phosphoric acid.
Another object of this invention is to provide an improved process for effectively removing iron from phosphoric acid.
DETAILED DESCRIPTION OF THE INVENTION These and other objects of the invention are accomplished by the surprising discovery that by precipitating barium ions in the presence of sulphate ions from technical grade phosphoric acid there is also a substantial reduction in the amount of iron in the phosphoric acid. This discovery is even more astounding since iron ions are generally unable to form precipitates in strongly acid media with sulphate, phosphate or barium ions. While the theory is not completely understood, it is believed that the removal of iron ions from the phosphoric acid is accomplished by the mechanism of simultaneous precipitation along with the slightly soluble barium sulphate. It has been further discovered that the diminution in the iron content is not only dependent on the amount of precipitated barium sulphate but also on an excess of barium ions with respect to the sulphate ion content of the phosphoric acid whereby an increase in the amount of barium ions leads to a greater diminution in the amount of iron. In contrast, the simultaneous precipitation of iron with 'barium sulphate is quite independent of the concentration of the phosphoric acid. For procedural reasons, precipitation is carried out in dilute solutions, since it is known that the separation of a barium sulphate precipitate from concentrated viscous fluids is considerably difiicult and may even make separation impossible.
A further advantage of the present invention resides in the fact that precipitation of barium can be successfully conducted in phosphoric acid diluted with an organic solvent miscible with phosphoric acid and water in all proportions, such as water-soluble aliphatic alcohols and/ or ketones. Dilution of concentrated phosphoric acid with such an organic solvent facilitates separation of the precipitate, since it is easily filtered. The reconcentration of the purified phosphoric acid from such a diluted solution is accomplished with considerably less consumption of energy than when using water alone.
The amount of solvent in the phosphoric acid can vary over a wide range. It has been noted that the process works best if the P 0 content of the dilute phosphoric acid is between about 5 and 30 weight percent and the amount of solvent is between about 40 and 90 weight percent. 7
Since removal of iron from the phosphoric acid is carried out with an excess of barium ions based on the amount of sulphate ions, greater or lesser quantities of barium ions in the form of dissolved salts occur in the phosphoric acid to be purified, and thus results in a new contaminate to the phosphoric acid. However, in contrast to dissolved iron, dissolved barium ions are easily removed from the dilute phosphoric acid by use of a strongly acid cation exchange resin. Therefore, the dilute phosphoric acid solution, substantially free of barium and iron precipitates, is passed through one or more exchangers, after which the thus purified phosphoric acid can be steamed, and as circumstances require, the solvent distilled off.
The removal of iron from the phosphoric acid can in principle be accomplished with any water soluble barium compounds. Furthermore, slightly soluble barium compounds are suitable as cannot possibly form a solution but permit barium ions to dissolve into phosphoric acid. In practice, the barium compounds used include barium hydroxide, barium phosphate, barium carbonate and barium sulphide. The distinguishing features of the process according to the present invention is the removal of iron from phosphoric acid by precipitation with barium ions in the presence of sulphate ions. It is immaterial whether the phosphoric acid from which iron is to be removed has been produced by the wet process and pre-purified by a known phosphoric acid purification step, or whether the phosphoric acid is produced by the electrothermic reduc tion method and has sebsequently become contaminated with iron during storage, transportation and the like.
When treating unpurified thermic phosphoric acid, a sufficient amount of sulphate ions must be added to the acid to effect the precipitation of iron by barium ions, whereas when treating wet phosphoric acid, in most instances, the amount of sulphate ions remaining from such process is sufficient to form a precipitate with added barium ions. The precipitation process of the invention is not limited to phosphoric acids which contain the contaminants named, but may also be used in the treatment of other phosphoric acids containing other impurities as well as iron and sulphate ions. The amount of barium used is in excess with respect to the amount of sulphate. The effect achieved is dependent as much on the sulphate concentration as on an excess of barium ions. The amount of sulfate ions should be in the range of 0.01 to 0.5 weight percent with respect to the P 0 content of the phosphoric acid, and the amount of barium ions should be 2 to 20 times in excess of the amount of sulphate ions.
As hereinabove mentioned, the barium ions remaining in the acid because of the necessity of excess barium ions are removed from the acid by passing the acid through a strongly acid cation exchange resin after filtration. The thus purified phosphoric acid may be brought to final concentration, which in the case of organic solvents, is accomplished by distillation.
EXAMPLES OF THE INVENTION The following examples are illustrative of conditions for the process of the invention and it is to be understood that the scope of the invention is not to be limited thereby.
Example I A technical grade phosphoric acid prepared by the wet process subsequently purified contains 52 weight percent P 0 0.05 weight percent Fe ions and 0.2 weight percent H 80 10 kilograms of this acid are diluted with 20 kilograms of acetone with 200 grams of dry barium carbonate thereafter introduced with vigorous stirring. After a period of 5 minutes, the precipitate is separated from the filtrate by filtration and the filtrate passed through a strongly acid cation exchange resin in the H+ form and is subsequently distilled. In the distillation vessel there remained 9.3 kilograms of a phosphoric acid having a P 0 content of 53.0 weight percent, an iron content of 0.003 weight percent and a sulphate content of 0.001 weight percent.
Example II Phosphoric acid produced by the thermic process and contaminated with iron ions through improper storage had a P 0 content of 54 weight percent and an iron content of 0.01 weight percent. 10 kilograms of the acid diluted with 50 kilograms of isopropanol was admixed with 5 grams of concentrated sulphuric acid. 1750 grams of an aqueous barium phosphate solution having a. barium content of 8.0% and a P 0 content of 19.0% was added with stirring to the phosphoric acid solution. After 10 minutes, the precipitate produced is separated from the solution by filtration. The clean filtrate is passed through a strongly acid cation exchange resin in the H+ form. The organic solvent is removed from the acid by distillation. 10.5 kilograms of a phosphoric acid having a P 0 content of 48.5 weight percent and a Fe iron content of 0.0007 weight percent are recovered.
Example III A technical grade phosphoric acid produced by the wet process and previously purified contains 48.0 weight percent P O 0.03 weight percent Fe and 0.1 weight percent H 50 10 kilograms of the acid are diluted with 30 kilograms of water. Into a stirred container, there are added 51 -grams of barium hydroxide dissolved in 200 milliliters of carbonatet-free water to the dilute phosphoric acid. After 10 minutes, the precipitate is separated from the solution by filtration with the filtrate being passed through a strongly acid cation exchange resin in the H+form. The filtration time is limited. 11.0 kilograms of a phosphoric acid are recovered with a P 0 content of 41 weight percent and a Fe content of 0.0015 weight percent. Sulphate ions are not demonstrable.
Numerous modifications and variations of the invention are possible in light of the above teachings and therefore the invention may be practiced otherwise than as particularly described.
What is claimed is:
1. A process for removing iron ions from phosphoric acid having iron and sulfate ions which comprises:
(a) diluting phosphoric acid having a P 0 content of between 5 to 30 weight percent with an organic solvent selected from the group consisting of water soluble aliphatic alcohols and ketones and miscible with phosphoric acid and water in all proportions;
(b) adding barium ions to the solution resulting from step (a), the amount of barium ions added being of from two to twenty times in excess of the amount necessary to precipitate the sulfate ions whereby a precipitate is formed; and
(c) separating the precipitate from the liquor.
(d) separating the organic solvent from the liquor and recovering phosphoric acid.
2. The process as defined in claim 1 wherein the barium compound acting as a source of barium ions is selected from the group comprising barium carbonate, barium phosphate, barium hydroxide and barium sulfide.
3. The process as defined in claim 1 wherein the phosphoric acid is diluted with water prior to step (a).
4. The process as defined in claim 1 wherein the phosphoric acid is diluted with an organic solvent miscible with phosphoric acid and water in all proportions in an amount of from 40 to weight percent.
5. The process as defined in claim 1 wherein the sulfate ion is present in a concentration of from 0.01 to 0.5 weight percent with respect to the P 0 content of the phosphoric acid.
References Cited UNITED STATES PATENTS 2/1968 Schallert et a1 23----165 X 1/1971 Barker et a1 23-165 X 6 2,044,940 6/1936 Haag et a1 23165 X 3,33 8,675 9/1967 Gilbert 23-165 FOREIGN PATENTS 552,756 12/1956 Belgium 23.165
OSCAR R. VERTIZ, Primary Examiner G. A. HELLER, Assistant Examiner
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2047261A DE2047261C3 (en) | 1970-09-25 | 1970-09-25 | Process for removing iron from phosphoric acid |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3784678A true US3784678A (en) | 1974-01-08 |
Family
ID=5783392
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US00182240A Expired - Lifetime US3784678A (en) | 1970-09-25 | 1971-09-20 | Process for removing iron from phosphoric acid |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US3784678A (en) |
| BE (1) | BE772743A (en) |
| DE (1) | DE2047261C3 (en) |
| FR (1) | FR2108490A5 (en) |
| GB (1) | GB1314281A (en) |
| IT (1) | IT938820B (en) |
| NL (1) | NL7113054A (en) |
| SE (1) | SE370380B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4041134A (en) * | 1976-02-13 | 1977-08-09 | Toyo Soda Manufacturing Co., Ltd | Process for removing sulfate ions from extracted phosphoric acid employing barium compounds and activated carbon |
| US4190634A (en) * | 1978-05-08 | 1980-02-26 | Monsanto Company | Purifying phosphoric acid by extraction with an aliphatic nitrile |
| US4263265A (en) * | 1978-09-29 | 1981-04-21 | Rhone-Poulenc Industries | Process for obtaining a desulfated phosphoric acid for use in foods and beverages |
| US20230365409A1 (en) * | 2021-02-25 | 2023-11-16 | Jesa Technologies Llc | Method for removing heavy metals in the manufacture of phosphoric acid |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4070443A (en) * | 1976-02-13 | 1978-01-24 | Toyo Soda Manufacturing Co., Ltd. | Process for removing sulfate ions from extracted phosphoric acid with a barium compound |
-
1970
- 1970-09-25 DE DE2047261A patent/DE2047261C3/en not_active Expired
-
1971
- 1971-09-06 GB GB4136171A patent/GB1314281A/en not_active Expired
- 1971-09-17 FR FR7134330A patent/FR2108490A5/fr not_active Expired
- 1971-09-17 BE BE772743A patent/BE772743A/en unknown
- 1971-09-20 US US00182240A patent/US3784678A/en not_active Expired - Lifetime
- 1971-09-20 IT IT28836/71A patent/IT938820B/en active
- 1971-09-23 NL NL7113054A patent/NL7113054A/xx unknown
- 1971-09-24 SE SE7112120A patent/SE370380B/xx unknown
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4041134A (en) * | 1976-02-13 | 1977-08-09 | Toyo Soda Manufacturing Co., Ltd | Process for removing sulfate ions from extracted phosphoric acid employing barium compounds and activated carbon |
| US4190634A (en) * | 1978-05-08 | 1980-02-26 | Monsanto Company | Purifying phosphoric acid by extraction with an aliphatic nitrile |
| US4263265A (en) * | 1978-09-29 | 1981-04-21 | Rhone-Poulenc Industries | Process for obtaining a desulfated phosphoric acid for use in foods and beverages |
| US20230365409A1 (en) * | 2021-02-25 | 2023-11-16 | Jesa Technologies Llc | Method for removing heavy metals in the manufacture of phosphoric acid |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2108490A5 (en) | 1972-05-19 |
| DE2047261A1 (en) | 1972-03-30 |
| DE2047261B2 (en) | 1974-11-28 |
| GB1314281A (en) | 1973-04-18 |
| IT938820B (en) | 1973-02-10 |
| DE2047261C3 (en) | 1975-07-17 |
| BE772743A (en) | 1972-01-17 |
| NL7113054A (en) | 1972-03-28 |
| SE370380B (en) | 1974-10-14 |
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